1. Field of the Invention
This invention relates to a numerically controlled apparatus, and more particularly to a numerically controlled apparatus which can make a retrograding operation.
2. Description of the Prior Art
A numerically controlled apparatus having a so-called retrograding function is already known wherein the process of working retrogrades along a working route in response to reception of a retrograding command during working.
FIG. 18 shows an exemplary one of conventional numerically controlled apparatus having a retrograding function. Referring to FIG. 18, the numerically controlled apparatus shown includes an interpolation pre-processing section 2 for receiving a working program stored in a working program storage medium 1 and composed of a plurality of command blocks, a retrograde block processing section 3 for selecting information necessary for the production of a retrograde block command in accordance with the working program received from the interpolation pre-processing section 2, an interpolation processing section 4, an acceleration/deceleration controlling section 5, a feeding device 6, a retrograding processing section 7, and a retrograde stock storage section 8.
In operation, the interpolation pre-processing section 2 reads the working program block by block from the working program storage medium 1 and outputs data of an amount of the feeding device 6 to move, a position of a starting point, a position of an ending point, a feeding speed and so forth to the interpolation processing section 4 by way of the retrograde block processing section 3.
The interpolation processing section 4 executes interpolation processing in accordance with the data outputted from the interpolation pre-processing section 2 and outputs a result of the interpolation processing to the acceleration/deceleration processing section 5.
The acceleration/deceleration processing section 5 thus controls a tool not shown to move in accordance with the result of the interpolation processing of the interpolation processing section 4, thereby to work a work not shown.
By the way, during such working of a work, the working may sometimes be interrupted by some cause such as hitting by a stroke of lightning. In such an instance, the tool will be moved back using a retrograding function of the numerically controlled apparatus.
To this end, the retrograde block processing section 3 stores, during working of a work, in accordance with results of decoding of block commands, necessary data for the interpolation for a retrograding operation such as a starting point of each block command and a command speed as well as, when a block command is based on a circular interpolation, coordinates of the center, a radius and so forth of a circle into the retrograde block storage section 8 in accordance with the order of decoding of the block commands. Then, when a retrograding signal is received in response to interruption of working, the retrograde block processing section 3 successively reads out the data stored in the retrograde block storage section 8 in an order reverse to the order in storage of the data to cause the interpolation processing section 4 to execute an operation in accordance with the read out data. Consequently, the route along which the working has been carried out is interpolated reversely to return the tool to a suitable point of the route.
Referring now to FIG. 19, there is shown another exemplary one of conventional numerically controlled apparatus. The numerically controlled apparatus shown includes a working program processing section 12 for reading a working program from a working program storage medium 11 and decoding the the working program thus read, a mechanical controlling section 13 for producing numerically controlling commands (commands for moving individual axes, speed commands and mechanical sequence controlling commands) from data of the working program decoded by the working program processing section 12 and external mechanical controlling signals, an interpolation pulse distributor 14 for interpolating commands for the axes from the mechanical controlling section 13, a pair of servo controlling sections 15 for individually driving servomotors 16 for the axes, a mechanical input/output processing section 17 for transmitting and receiving signals to and from a mechanical and strong electric circuit section not shown, a setting section 42 for setting and storing in advance therein as a parameter a retracting position to which a tool not shown is to be retracted upon interruption of working, and a retraction controlling section 43 for executing retracting control of the tool in response to an external signal.
In operation, when an operation starting signal is received, the mechanical controlling section 13 commands the working program processing section 12 to read the working program.
The working program processing section 12 thus reads out and decodes the working program for each block from the working program storage medium 11 and outputs axis command data and sequence controlling commands to the interpolation pulse distributor 14 and the mechanical input/output processing section 17 by way of the mechanical controlling section 13.
The interpolation pulse distributor 14 controls the servo controlling sections 15 in accordance with the received axis command data to control driving of the servomotor 16s. Meanwhile, the mechanical input/output processing section 17 executes sequence control in accordance with the sequence control commands received.
After then, such decoding of the working program, outputting of axis command data and sequence control commands as well as axis control and sequence control as described above are executed repetitively to work the work not shown.
In case the working is interrupted due to emergency stopping or the like during such working, the tool not shown is retracted from the work. Then, when a returning signal is received, the retraction controlling section 43 gives up the working which has been carried out so far and produces and outputs to the mechanical controlling section 13 a returning command for returning the tool from a position upon such interruption to a retracted position set by the setting section 42.
By the way, a sub program of a so-called fixed cycle is sometimes executed wherein a series of routine sequences which are naturally programmed in several blocks are commanded in a single block so as to simplify programming of a working program.
FIG. 20 schematically shows a numerically controlled apparatus which executes such a sub program of a fixed cycle as described above. In FIG. 20, like elements having like functions to those of FIG. 19 are denoted by like reference numerals and overlapping description thereof is omitted herein.
Referring to FIG. 20, the numerically controlled apparatus shown includes, in addition to a working program processing section 12, a mechanical controlling section 13, an interpolation pulse distributor 14, a pair of servo controlling sections 15 and a mechanical input/output processing section 17, a memory 18 having sub programs of a fixed cycle stored therein, another memory 52 having stored therein tool retracting programs which are produced for individual fixed cycle commands taking a profile of a work into consideration in advance, and a retraction controlling section 53 for executing, when a returning signal is received from an outside, retracting control in accordance with contents stored in the memory 52.
The numerically controlled apparatus shown in FIG. 20 normally operates in a similar manner to that shown in FIG. 19.
On the other hand, when working is interrupted due to emergency stopping or the like while an operation of a fixed cycle is being executed, a tool not shown is retracted from a work not shown. Then, when a returning signal is received, the retraction controlling section 53 gives up the working and executes the tool extracting program for the interruption of a fixed cycle stored in the memory 52 to produce and output movement commands to the mechanical controlling section 13. The mechanical controlling section 13 executes the movement commands to retract the tool to a position at which the operation of the fixed cycle has been started.
By the way, with the conventional numerically controlling apparatus shown in FIG. 18, since a tool is retracted, upon retrograding movement, while it is held in contact with a work, there is a problem that the work is likely to be damaged and, depending upon a type of the tool, the chip of the tool may be damaged. It is also disadvantageous in that, since the speed of retracting movement is equal to the speed upon cutting, much time is required for such retracting movement.
Meanwhile, with the conventional numerically controlled apparatus shown in FIG. 19, there is a problem that, if a tool is returned to a retracted position set in advance, then, depending upon a working route of the tool, a profile of a work or the like, the tool may interfere with the work and cannot be returned readily.
Further, with the conventional numerically controlled apparatus shown in FIG. 20, there is a problem that a retraction program must be produced for each fixed cycle taking a profile of a work into consideration in advance, and the programming steps are increased.